Without limiting the scope of the invention, its background is described in connection with the treatment of plants against pathogens.
In recent years research and development efforts for the treatment of plant pathogens has focused on two main approaches, chemical and genetic. Over the years, more and more powerful chemical agents have been developed and refined to prevent and treat plants. These chemical agents are designed or isolated to affect a critical reproductive step in the growth, maturation or division of the target organism. However, more often than not, the chemical agent has an effect on other plants and animals.
An alternative approach has been to genetically modify the plant itself. For crops this has been a useful technique as the newly modified plants may be introduced in the next crop cycle and monitored. The chemical and genetic have even been used in combination by modifying the plant to resist certain chemicals that the pathogens can not.
Examples of methods for protecting fruits may be found in U.S. Pat. No. 4,946,694, issued to Gunnerson, et al., for a “Liquid coating for fruits.” These inventors teach an improved coating for sticky fruits and a process for preparing such coated fruits. More particularly, the coating of the invention comprises a vegetable wax, a vegetable oil, a wetting agent and a protein. The process is said to include the steps of: (a) coating the fruit with a composition that includes a wetting agent and a suspension of a vegetable wax in a vegetable oil, (b) adding to the fruit a composition with a protein, (c) removing excess mixture from the fruit, and (d) drying the fruit. However, the addition of protein greatly increases the cost of the application and provides a potential substrate for attachment.
Yet another chemical coating is taught in U.S. Pat. No. 4,039,470, issued to Kalmar, entitled “Preservative coating for fruits and vegetables.” This inventor coats fruits with a finely atomized spray of an acid solution of benzimidazole that must be retained in a separate corrosion resistant chamber prior to being mixed with the wax or resin solution just prior to application.
Yet another coating is taught in U.S. Pat. No. 4,783,342, issued to Polovina and entitled, “Polymeric film coating method for protecting plants, vegetables and fruit from drought,” which relates to a method of preserving plants during periods of drought by applying a solid, water permeable film which controls water loss, to the surface of the plants. The same film can also be used to preserve vegetables and fruit. The water permeable film is also effective to preserve cut flowers.
Finally, U.S. Pat. No. 5,922,774, issued to Winslow teaches a method for controlling plant damage by insect herbivores. Briefly, this patent teaches using chemically-synthesized anthraquinones to repelling insect herbivores from plant surfaces and deterring them from feeding on plant surfaces by applying an aqueous dispersion of polycyclic quinone or precursor thereof to the foliage of the plant and/or to the surrounding soil in which the plant is rooted.
Despite the many efforts in this regard, nature finds a way to circumvent and select for those pathogens that are no longer resistant to the chemical or the genetic modification. Furthermore, these methods are most useful for those crops and plants that are replaced seasonally or yearly. Trees, plants and crops that live for many years before replacement, however, are unable to benefit from the genetic manipulation. Furthermore, many, many trees, plants and crops have not been able to be readily manipulated. These plants are still in need of protection and treatment from pathogens without an effect on the local environment, plants and fauna.